In recent years, for example, a small-sized simple glucose level measuring apparatus using an electrode type of biosensor has been used to diagnose a glucose level of diabetics and has been used in daily management. FIG. 4 is an exploded perspective view illustrating an example of a structure of a glucose sensor, and silver leads 4 and 5 are formed by a screen printing or the like on an insulating substrate 7 of PET (Polyethylene Terephthalate).
A quadrangular working electrode 1 is formed by carbon on the tip of the silver lead 4, and a counter electrode 2 is formed so as to have a predetermined gap between the silver lead 5 and the working electrode 1 on the tip of the silver lead 5 and surround the working electrode 1. Terminal parts 4a and 5a connected to a measuring device at the measurement are formed on the other ends of the silver leads 4 and 5, respectively. On both electrodes 1 and 2 so formed, a reaction layer 12 comprising a CMC (Carboxyl Methyl Cellulose) layer which is a hydrophilic polymer, GOD (Glucose Oxidase) as an enzyme, and potassium ferricyanide as a mediator is formed so as to bridge and cover both of the electrodes 1 and 2.
Further, a cover 8 on the tip of which a sample supplying groove 10 having an opening 9 is formed over the layer 12 is attached on the substrate 7 such that an end part of the sample supplying groove 10 is located on the reaction layer 12, and an air hole 11 is formed on an end part of the sample supplying groove 10.
When the sensor so constructed is mounted on the small-sized simple measuring apparatus for measuring glucose level and then blood sample to be measured comes in contact with the opening 9 of the sample supplying groove 10, a fixed quantity (approximately 3 μL) of the sample is introduced into the reaction layer 12 by capillary action via the sample supplying groove 10, whereby predetermined reaction occurs. A current value accompanying the reaction is read on the measuring apparatus side through the terminal parts 4a and 5a, and the content of glucose as a substance to be measured is measured from the current value.
In the small-sized simple measuring apparatus as described above, recently, the emphasis has been, more particularly, on the field of data management such as the management and'processing of the measurement data, and, for example, the apparatus is constructed such that the measuring apparatus successively stores a measured value and can easily ascertain variations per hour, an average value or the like. Further, when accurate data management is made, it is required to maintain and manage the accuracy of the biosensor and the measuring apparatus. Therefore, the apparatus regularly measures using an exclusive glucose standard solution, thereby performing accuracy management thereof.
When the accuracy of the measuring apparatus is maintained and managed, a specified manual operation is performed on the measuring apparatus beforehand so as not to confuse the measurement data for accuracy management using the exclusive glucose standard solution with the measurement data using blood normally used as a sample, and switching is performed to a standard solution measurement mode when the measurement is made by the standard solution, where the apparatus is devised so as to discriminate between the blood measurement data and the exclusive glucose standard solution measurement data or the like.
However, when a manual preoperation is necessary in the measuring apparatus, data is managed in a state where the standard solution measurement data is incorrectly recognized as the blood measurement data due to an artificial incorrect operation, a forgotten operation or the like. More particularly, it is difficult for users having trouble with their eyes and fingers to perform the preoperation as described above, and therefore, a system which can automatically judge types of sample solution without operations has been desired.
The present invention is made to solve the above-described problems and has, for its object, to provide a measuring apparatus which can automatically judge types of sample solution without artificial operations, a biosensor used therefor, and an exclusive standard solution.